Ultra-Wideband DesignGuide

Transcription

1 Ultra-Wideband DesignGuide January 2007

2 Notice The information contained in this document is subject to change without notice. Agilent Technologies makes no warranty of any kind with regard to this material, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. Agilent Technologies shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material. Warranty A copy of the specific warranty terms that apply to this software product is available upon request from your Agilent Technologies representative. Restricted Rights Legend Use, duplication or disclosure by the U. S. Government is subject to restrictions as set forth in subparagraph (c) (1) (ii) of the Rights in Technical Data and Computer Software clause at DFARS for DoD agencies, and subparagraphs (c) (1) and (c) (2) of the Commercial Computer Software Restricted Rights clause at FAR for other agencies. Agilent Technologies, Inc Page Mill Road, Palo Alto, CA U.S.A. Acknowledgments Mentor Graphics is a trademark of Mentor Graphics Corporation in the U.S. and other countries. Microsoft, Windows, MS Windows, Windows NT, and MS-DOS are U.S. registered trademarks of Microsoft Corporation. Pentium is a U.S. registered trademark of Intel Corporation. PostScript and Acrobat are trademarks of Adobe Systems Incorporated. UNIX is a registered trademark of the Open Group. Java is a U.S. trademark of Sun Microsystems, Inc. SystemC is a registered trademark of Open SystemC Initiative, Inc. in the United States and other countries and is used with permission. MATLAB is a U.S. registered trademark of The Math Works, Inc. ii

3 Contents 1 Ultra-Wideband DesignGuide Introduction Pulse Mode Test Benches Spectrum Simulation Results Modulated Transmit Spectrum Simulation Results Receiver Sensitivity Eb/No Bi-Phase Modulation Simulation Results Pulse Position Modulation Simulation Results Receiver Sensitivity with Interference Sources Narrow Band Interference Simulation Results Wide Band Interference Simulation Results BER versus Range Simulation Results Synchronization Simulation Results Rake Receiver Simulation Results Pulse Mode Test Bench Component Details BAND_LIMITED_NOISE_SOURCE_UWB_Channel BiPhase_Polarity_Select_UWB_Transmitter BIPHASE_RX_REFERENCE_PULSER BIPHASE_TX_PULSE_GENERATOR INTERFERENCE_SOURCE_80211a_UWB_Channel INTERFERENCE_SOURCE_80211B_UWB_Channel MultipathDelayBlock_UWB_Channel PPM_MOD_UWB_Transmitter PPM_RX_Reference_Pulser PPM_TX_Pulse_Generator PropagationLoss PULSE_SHAPE_GENERATOR PULSE_TRIGGER_UWB_Transmitter Rake_Finger_UWB_Receiver Ref_Pulser_Shaping_Filters iii

4 Index Sync_Coarse_UWB_Receiver Sync_Fine_Tune_UWB_Receiver UWB_BIT_SLICER_UWB_Receiver UWB_ENVIRONMENT UWB_Interference_Source UWB_RAKE_BIT_SLICER_UWB_Receiver UWB_RECEIVE_ANTENNA UWB_RX_Correlator_UWB_Receiver UWB_RX_Correlator_with_Integrator_Reset_UWB_Receiver UWB_RX_LNA UWB_RX_SINGLE_FINGER_CORRELATOR UWB_Rake_Receiver_Correlator UWB_TRANSMIT_ANTENNA iv

5 Chapter 1: Ultra-Wideband DesignGuide Introduction The Ultra-Wideband DesignGuide test benches provide rapid setup, analysis, and simulation results to verify the most common performance characteristics of UWB transmitters and receivers. Bi-phase and pulse-position UWB modulation and formats are supported. Simulation results provide information for spectral characteristics and basic bit-error-rate versus signal-to-noise ratios, as well as environmental effects such as multi-path and propagation loss, allowing the BER to be determined as a function of range. Simulations also evaluate rake receiver performance in a multi-path environment and synchronization of a UWB correlator. Effects of narrowband and wideband interference on UWB system performance can also be evaluated. The UWB DesignGuide requires the ADS Ptolemy (signal processing simulation) and dg_ultrawideband licenses in addition to the ADS design environment license. The Analog/RF linear simulator can be used to generate S-parameter files for antennas, but is not required. S-parameter files can be obtained via network analyzer measurements or other sources. Features and contents of the UWB DesignGuide are accessible from the DesignGuide menu in an ADS Schematic window. Selecting a test bench copies a schematic into the current project and opens a Data Display window. Hints regarding this DesignGuide Information about items in a Data Display window that you would want to modify is outlined in red. Equations that you typically do not need to modify are often included in a separate Equations page. After selecting an item that opens Schematic and Data Display windows, if you re-name the schematic and run a simulation, to display your latest simulation results open the data display file that corresponded to the original schematic, change the default dataset name (typically the same as the new name of your schematic). Introduction 1-1

6 Ultra-Wideband DesignGuide 1-2 Introduction

7 Chapter 2: Pulse Mode Test Benches Spectrum The distribution of energy in the UWB spectrum is primarily determined by the spectrum corresponding to the shape of the individual pulses. The Spectrum Test Bench provides simulations of the spectrum of a single UWB pulse; the schematic for this test bench is shown in Figure 2-1. Figure 2-1. Spectrum Test Bench (_UWB_Pulse_Spectrum.dsn) Standard pulse shapes, as well as amplitudes and widths, can be selected; for details, refer to PULSE_SHAPE_GENERATOR on page The transmit filter represents the effects of transmitter front-end and antenna; for details, refer to UWB_TRANSMIT_ANTENNA on page The SpectrumAnalyzer Filter_Output_Spectrum component is configured to have a resolution bandwidth of 1 MHz; Filter_Output_Spectrum_Peak is configured to have a resolution bandwidth of 50 MHz. The 50 MHz resolution bandwidth single pulse spectrum shows whether a UWB transmitter with a pulse rate less than 50 MHz complies with FCC regulations for peak radiated power. Spectrum 2-1

8 Pulse Mode Test Benches Spectrum Test Bench Design Parameters Name TStep PulseEnergy_joule PulseWidth DoubletSeparation Description Time step of the simulation. It should be approximately PulseWidth/10 Total energy of the single pulse in Joules. For the doublet pulse shape, this is the energy of each individual monopulse making up the doublet. Total doublet energy is twice this value. Width of output pulse Time between the positive and negative peaks of the waveform when the GAUSSIAN_DOUBLET_UWB_TRANSMITTER subnetwork of PULSE_SHAPE_GENERATOR is active. 2-2 Spectrum

9 Simulation Results The Data Display window shows the spectrum before and after a transmit filter is applied; pulse shapes before and after filtering are also shown. The transmit spectrum with 50 MHz resolution bandwidth shows compliance with FCC regulatory limits for peak indoor UWB radiation. Spectrum 2-3

10 Pulse Mode Test Benches Modulated Transmit Spectrum The shape of the spectrum is primarily determined by the spectrum corresponding to the shape of the UWB pulses. The distribution of energy into narrow bandwidth spectral lines is determined by the transmitter pulse rate and modulation. The Modulated Transmit Spectrum Test Bench simulates the spectrum of a basic UWB signal with pulse position or bi-phase modulation; the schematic for this test bench is shown in Figure 2-2. Figure 2-2. Modulated Transmit Spectrum Test Bench (_UWB_Modulated_Transmit_Spectrum.dsn) To choose pulse position or bi-phase modulation, enable the PPM or bi-phase pulse generator component; deselect the unused component. Pulse shapes, as well as pulse rates, amplitudes, and widths can be selected. For details, refer to BIPHASE_TX_PULSE_GENERATOR on page 2-59 or PPM_TX_Pulse_Generator on page The transmit filter represents the effects of transmitter front-end and antenna; for details, refer to UWB_TRANSMIT_ANTENNA on page A pseudorandom bit sequence is used as the spreading code for UWB modulation. For bi-phase modulation, one bit from the spreading code is consumed per transmitted pulse. The spreading code repeat time is equal to the pulse interval multiplied by the pseudorandom bit sequence length. For pulse position modulation, the value of DitherBits determines the number of spreading code bits consumed for each 2-4 Modulated Transmit Spectrum

11 transmitted pulse. The spreading code repeat time for pulse position modulation is the pulse interval multiplied by the spreading code length divided by the number of value of DitherBits. The spreading code repeat time determines the spacing of spectral lines in the modulated transmit spectrum. For the SpectrumAnalyzer Filter_Output_Spectrum component, the NPoints parameter is set equal to 1e-6/TStep; this corresponds to a sample time of 1 µsec or a resolution bandwidth of 1 MHz. The spectral power density can be compared to the FCC regulations for indoor UWB radiation. For example, for 3.1 to 10.6 GHz the maximum allowed spectral power density is dbm/mhz. The simulated average spectral power density in this frequency range must be less than this limit. Simulation length is determined by the DefaultTimeStop parameter. When this value is larger, the output spectrum will have less deviation because it is averaged over more sample times. Modulated Transmit Spectrum Test Bench Design Parameters Name ChipInterval ChipsPerBit DitherBits TStepsPerPulseWidth TStepsPerDither DithersPerPPMBitOffset TStepsPerPPMBitOffset DitherTime TStep PulseWidth DoubletSeparation PulseEnergy_joule Description Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit Number of bits used to the dither position of a PPM pulse within each pulse interval. 2 DitherBits pulse positions are possible within each PPM pulse interval. Approximate number of simulation time steps in one pulsewidth interval. Determines the number of simulation time steps between each possible position. Number of dither positions offset between a value of 1 and 0 in a PPM modulated code. Length is given in the number of dither intervals in the offset time. This makes the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Number of TStep offset between a value of 1 and a 0 in a PPM modulated code. Length is given in the number of TStep long intervals in the offset time. (For pulse position modulation.) Time between possible dither positions in a PPM pulse interval. (For pulse position modulation.) Time step of the simulation. It is an integer division of the ChipInterval. It is approximately PulseWidth/10 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. Time between the positive and negative peaks of the waveform when doublet pulse is used. (Used when doublet waveform is selected.) Energy in Joules of a single pulse output from the pulse generator. Modulated Transmit Spectrum 2-5

12 Pulse Mode Test Benches Simulation Results The Data Display window shows the transmit spectrum before and after a transmit filter is applied. The transmit spectrum is compared to the FCC regulatory limit for indoor UWB radiation. Transmit pulse shapes before and after filtering are also displayed. Calculations of power in dbm/mhz over a user-selectable band are displayed. 2-6 Modulated Transmit Spectrum

13 Receiver Sensitivity Eb/No The Bi-Phase and Pulse Position Modulation test benches simulate the bit-error-rate of a basic UWB transmitter and receiver as a function of receiver signal-to-noise ratio. Basic BER vs. signal-to-noise ratio can be investigated using this simulation (antenna and environmental effects are not included). The time required for a simulation to run is dependent on TStep and the length of time simulated. TStep, determined by the PulseWidth value, is approximately 1/10th PulseWidth. The length of time simulated is the product of the number of bits simulated, the number of chips per bit, and the time interval per chip. Example simulation times using a 1500 MHz Pentium IV processor are: For a chip rate of 1 GHz using 5 chips per bit, bits can be simulated in 200 seconds when PulseWidth is 250 psec and TStep is psec. Simulation time is 50 µsec, so the simulation rate is 9000 TSteps per second. For a chip rate of 10 MHz using 5 chips per bit, 100 bits can be simulated in 285 seconds when PulseWidth is 250 psec and TStep is psec. The simulation rate is 8700 TSteps per second. Filters were not used in these simulations; adding filters with long impulse response times will increase the time for the simulation to complete. As time interval per chip increases, the simulation time for a fixed number of bits increases proportionally. A time compression technique can be applied in order to maximize the number of bits that can be simulated in a given simulator run time. This is necessary because, to accurately simulate BERs, the simulation must run until approximately 10 times 1/BER bits have been output from the receiver. In addition, the time step size of the simulation is determined by the pulse width. This means that it takes longer to simulate a number of bits when the pulse rate is low; however, at low pulse rates, there is essentially no interaction between pulses. And, because the correlator reference signal is 0 during the time between pulses, the receive signal between pulses can be assumed to have insignificant contribution to the integrator output signal. This means that the chip interval used in simulation can be reduced as much as possible before interaction between pulses becomes a factor. This can significantly reduce the run time of low duty-cycle pulse simulations. The StopBits variable determines the number of bits to be collected by the DataOutput sink. This controls the length of time required to run the simulation. To speed simulations that sweep the interfering noise power, StopBits can be defined in a VAR equation using the piecewise linear function so the number of bits simulated is 10 times the estimated 1/BER at that noise power. For high noise-power levels, the Receiver Sensitivity Eb/No 2-7

14 Pulse Mode Test Benches BER will be higher, and fewer bits are required to accurately determine the BER. At lower noise-power levels, simulation of more bits are required. The user can rely on information from previously completed simulations to configure the piecewise linear function. When the SpectrumAnalyzer and TimedSink components are active during a simulation sweep, the user can also use a piecewise-linear function to optimize the TimeStop variable for the sweep. Receiver Sensitivity Eb/No Design Parameters Name ChipInterval ChipsPerBit DitherBits TStepsPerDither Description Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit. Number of bits used to determine the dither position of a PPM pulse within each pulse interval. There are 2 DitherBits possible pulse positions within each PPM pulse interval. (For pulse position modulation.) This determines the number of simulation time steps between each possible position. DithersPerPPMBitOffset Length of offset between 1 and 0 in a PPM modulated code. Length is given in the number of dither interval long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) TStepsPerPPMBitOffset DitherTime TStep PulseWidth DoubletSeparation PulseEnergy_joule NoiseBandWidthRatio NoisePower_dBm StopBits TimeStop Length of offset between 1 and 0 in a PPM modulated code. Length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Time between possible dither positions in a PPM pulse interval. (For pulse position modulation.) Time step of the simulation. It is an integer division of the ChipInterval. It is approximately PulseWidth/10. 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. time between the positive and negative peaks of the waveform when the GAUSSIAN_DOUBLET_UWB_TRANSMITTER subnetwork of PULSE_SHAPE_GENERATOR is active. Energy in Joules of a single pulse output from the pulse generator. Ratio of the simulation bandwidth to the noise bandwidth of the band limited noise source. The bandwidth is of the band limited noise source is 1/(2 NoiseBandWidthRatio TStep). Total power of bandwidth limited noise source in dbm. Number of bits simulated. Length of time SpectrumAnalyzer components collect data. 2-8 Receiver Sensitivity Eb/No

15 Bi-Phase Modulation The Bi-Phase Modulation Test Bench is shown in Figure 2-3 (transmitter section) and Figure 2-4 (receiver section). Representative pulse shapes can be selected. For component details, refer to BIPHASE_TX_PULSE_GENERATOR on page A pseudorandom code is used to spread the transmit data. Band-limited noise is added to the transmit signal before it enters the receiver. For component details, refer to BAND_LIMITED_NOISE_SOURCE_UWB_Channel on page The BIPHASE_RX_REFERENCE_PULSER component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when the data input is all 1s. The waveform output from this test block represents a bi-phase modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to BIPHASE_RX_REFERENCE_PULSER on page Simulations can sweep the noise power level relative to that of the transmit signal. The receiver correlator de-spreads the input UWB signal and the data bit stream is recovered from the correlator output. For component details, refer to UWB_RX_Correlator_UWB_Receiver on page The bit slicer captures the correlator integrator output value immediately before the integrator resets. This value is used to determine whether the output is a 0 or 1 bit. For component details, refer to UWB_BIT_SLICER_UWB_Receiver on page Receiver Sensitivity Eb/No 2-9

16 Pulse Mode Test Benches To Receiver Section Figure 2-3. Bi-Phase Modulation Test Bench, Transmitter Section (_UWB_Biphase_Bench.dsn) 2-10 Receiver Sensitivity Eb/No

17 Figure 2-4. Bi-Phase Modulation Test Bench, Receiver Section (_UWB_Biphase_Bench.dsn) Receiver Sensitivity Eb/No 2-11

18 Pulse Mode Test Benches Simulation Results For bi-phase modulation, the Data Display window shows the transmit pulse train over two time scales. The receiver input signal plot shows the transmit signal combined with interfering noise. The spectra of the transmit signal and interfering noise are also shown. Bit errors are determined by comparing the data bits input to the transmitter to those output from the receiver. A BER vs. signal-to-noise ratio plot (labeled Eb/No) shows how BER is degraded by the interfering noise Receiver Sensitivity Eb/No

19 Receiver Sensitivity Eb/No 2-13

20 Pulse Mode Test Benches Pulse Position Modulation The Pulse Position Modulation Test Bench is shown in Figure 2-5 (transmitter section) and Figure 2-6 (receiver section). Representative pulse shapes can be selected. For component details, refer to PPM_TX_Pulse_Generator on page A pseudorandom code is used to spread the transmit data. Band-limited noise is added to the transmit signal before it enters the receiver. For component details, refer to BAND_LIMITED_NOISE_SOURCE_UWB_Channel on page The PPM_RX_Reference_Pulser component outputs a waveform that is the sum of the pulse waveform produced by PPM_TX_Pulse_Generator when the data input is 1 with the inverse of the output when the data input is 0. The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to PPM_RX_Reference_Pulser on page Simulations can sweep the noise power level relative to that of the transmit signal. The receiver correlator de-spreads the input UWB signal and the data bit stream is recovered from the correlator output. For component details, refer to UWB_RX_Correlator_UWB_Receiver on page The bit slicer captures the correlator integrator output value immediately before the integrator resets. This value is used to determine whether the output is a 0 or 1 bit. For component details, refer to UWB_BIT_SLICER_UWB_Receiver on page Receiver Sensitivity Eb/No

21 To Receiver Section Figure 2-5. Pulse Position Modulation Test Bench, Transmitter Section (_UWB_PPM_Bench.dsn) Receiver Sensitivity Eb/No 2-15

22 Pulse Mode Test Benches Figure 2-6. Pulse Position Modulation Test Bench, Receiver Section (_UWB_PPM_Bench.dsn) 2-16 Receiver Sensitivity Eb/No

23 Simulation Results For pulse position modulation, the Data Display window shows the transmit pulse train over two time scales. The receiver input signal plot shows the transmit signal combined with interfering noise. The spectra of the transmit signal and interfering noise are also shown. Bit errors are determined by comparing the data bits input to the transmitter to those output from the receiver. A BER vs. signal-to-noise ratio plot (labeled Eb/No) shows how BER is degraded by the interfering noise. Receiver Sensitivity Eb/No 2-17

24 Pulse Mode Test Benches 2-18 Receiver Sensitivity Eb/No

25 Receiver Sensitivity with Interference Sources Narrow Band Interference The Narrow Band Interference Test Bench simulates a UWB transmitter and receiver with interference from an a/g or b signal source. Simulations can sweep the interference power level relative to that of the transmit signal. A correlator de-spreads and bit slices the received UWB signal. The receiver outputs the demodulated bit stream. The transmitter section of the test bench is shown in Figure 2-7; the receiver section of the test bench is shown in Figure 2-8. Receiver Sensitivity with Interference Sources 2-19

26 Pulse Mode Test Benches To Receiver Section Figure 2-7. Narrow Band Test Bench, Transmitter Section (_UWB_Narrow_Band_Interference.dsn) 2-20 Receiver Sensitivity with Interference Sources

27 Figure 2-8. Narrow Band Test Bench, Receiver Section (_UWB_Narrow_Band_Interference.dsn) Receiver Sensitivity with Interference Sources 2-21

28 Pulse Mode Test Benches A pseudorandom code is used to spread the transmit data. Pulse shapes, as well as pulse rates, amplitudes, and widths can be selected. To choose pulse position or bi-phase modulation, enable the PPM or bi-phase pulse generator component; deselect the unused component. For component details, refer to BIPHASE_TX_PULSE_GENERATOR on page 2-59 or PPM_TX_Pulse_Generator on page To choose the interference source, enable the B or a source component; deselect the unused component. The waveform for the a source is read from data set file WLAN_80211a_Order11.ds; for component details, refer to INTERFERENCE_SOURCE_80211a_UWB_Channel on page The waveform for the b source is read from data set file WLAN_80211b_8Xoversample.ds; for component details, refer to INTERFERENCE_SOURCE_80211B_UWB_Channel on page For bi-phase modulation, the BIPHASE_RX_REFERENCE_PULSER component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when data input is all 1s. The output represents a bi-phase modulated UWB waveform. Input data bits are spread using a spreading code. For component details, refer to BIPHASE_RX_REFERENCE_PULSER on page For pulse position modulation, the PPM_RX_Reference_Pulser component outputs the same waveform as PPM_TX_Pulse_Generator when the data input is 1 with the inverse of the output when the data input is 0. The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to PPM_RX_Reference_Pulser on page UWB_RX_Correlator_UWB_Receiver provides multiple correlators for receiving arrivals of a multipath signal. Each correlator multiplies the receive signal by an appropriately delayed reference signal. The integrator in the correlator integrates the multiplier output signal over the period of ChipInterval ChipsPerBit. It resets the integrator value to 0 and restarts the integration. The outputs of each correlator are scaled relative to its signal-to-noise ratio, and the outputs of all correlators are summed. For component details, refer to UWB_RX_Correlator_UWB_Receiver on page The bit slicer captures the correlator integrator output value immediately before the integrator resets. This value is used to determine whether the output is a 0 or 1 bit. For component details, refer to UWB_BIT_SLICER_UWB_Receiver on page Receiver Sensitivity with Interference Sources

29 Narrow Band Interference Test Bench Design Parameters Name ChipInterval ChipsPerBit DitherBits TStepsPerDither DithersPerPPMBitOffset TStepsPerPPMBitOffset DitherTime TStep PulseWidth DoubletSeparation PulseEnergy_joule NoiseBandWidthRatio NoisePower_dBm wlanpower_dbm StopBits TimeStop Description Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit Number of bits used to determine the dither position of a PPM pulse within each pulse interval. There are 2 DitherBits possible pulse positions within each PPM pulse interval. (For pulse position modulation.) Determines the number of simulation time steps between each possible position. Length of the offset between 1 and 0 in a PPM modulated code. Length is given in the number of dither interval long intervals in the offset time. This makes the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Length of offset between 1 and 0 in a PPM modulated code. Length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Time between possible dither positions in a PPM pulse interval. (For pulse position modulation.). Time step of the simulation. An integer division of ChipInterval; it is approximately PulseWidth/10 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. Time between the positive and negative peaks of the waveform when doublet pulse is used. (Used when doublet waveform is selected.) Energy in Joules of a single pulse output from the pulse generator Ratio of simulation bandwidth to noise bandwidth of the band limited noise source. The bandwidth is of the band limited noise source is 1/(2 NoiseBandWidthRatio TStep). Total power of bandwidth limited noise source in dbm. Center power of interfering WLAN source Number of bits simulated. Length of time SpectrumAnalyzer components collect data. Receiver Sensitivity with Interference Sources 2-23

30 Pulse Mode Test Benches Simulation Results The Data Display window shows the transmit pulse train over two time scales. The receiver input signal plot shows the transmit signal combined with the narrow band interference. The spectra of the transmit signal and the interfering noise are also shown Receiver Sensitivity with Interference Sources

31 Bit errors are determined by comparing the data bits input to the transmitter to those output from the receiver. An Eb/No plot shows how the bit error rate is degraded by the narrow band interference power. Receiver Sensitivity with Interference Sources 2-25

32 Pulse Mode Test Benches Wide Band Interference The Wide Band Interference Test Bench simulates a UWB transmitter and receiver with interference from another UWB transmitter. Simulations can sweep the interference power level relative to that of the transmit signal. A correlator de-spreads and bit slices the received UWB signal. The receiver outputs the demodulated bit stream. The transmitter section of the test bench is shown in Figure 2-9; the receiver section of the test bench is shown in Figure Receiver Sensitivity with Interference Sources

33 To Receiver Section Figure 2-9. Wide Band Interference Test Bench, Transmitter Section (_UWB_Wide_Band_Interference.dsn) Receiver Sensitivity with Interference Sources 2-27

34 Pulse Mode Test Benches Figure Wide Band Interference Test Bench, Receiver Section (_UWB_Wide_Band_Interference.dsn) 2-28 Receiver Sensitivity with Interference Sources

35 Pulse shapes, as well as pulse rates, amplitudes, and widths can be selected. To choose pulse position or bi-phase modulation, enable the PPM or bi-phase pulse generator component; deselect the unused component. For component details, refer to BIPHASE_TX_PULSE_GENERATOR on page 2-59 or PPM_TX_Pulse_Generator on page The interference source is a second UWB transmitter. For component details, refer to UWB_Interference_Source on page For bi-phase modulation, the BIPHASE_RX_REFERENCE_PULSER component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when the data input is all 1s. The output represents a bi-phase modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to BIPHASE_RX_REFERENCE_PULSER on page For pulse position modulation, the PPM_RX_Reference_Pulser component outputs the same waveform as PPM_TX_Pulse_Generator when the data input is 1 with the inverse of the output when the data input is 0. The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to PPM_RX_Reference_Pulser on page UWB_RX_Correlator_UWB_Receiver provides multiple correlators for receiving arrivals of a multipath signal. Each correlator multiplies the receive signal by an appropriately delayed reference signal. The integrator in the correlator integrates the multiplier output signal over the period of ChipInterval ChipsPerBit. It resets the integrator value to 0 and restarts the integration. The outputs of each correlator are scaled relative to its signal-to-noise ratio, and the outputs of all correlators are summed. For component details, refer to UWB_RX_Correlator_UWB_Receiver on page The bit slicer captures the correlator integrator output value immediately before the integrator resets. This value is used to determine whether the output is a 0 or 1 bit. For component details, refer to UWB_BIT_SLICER_UWB_Receiver on page Receiver Sensitivity with Interference Sources 2-29

36 Pulse Mode Test Benches Wide Band Interference Test Bench Design Parameters Name ChipInterval ChipsPerBit DitherBits TStepsPerDither DithersPerPPMBitOffset TStepsPerPPMBitOffset DitherTime TStep PulseWidth PulseEnergy_joule DoubletSeparation MaxFingerDelay NoiseBandWidthRatio NoisePower_dBm Interference_dBm StopBits TimeStop Description Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit. Number of bits used to determine the dither position of a PPM pulse within each pulse interval. There are 2 DitherBits possible pulse positions within each PPM pulse interval. (For pulse position modulation.) Determines the number of simulation time steps between each possible position. Length of offset between 1 and 0 in a PPM modulated code. The length is given in the number of dither long intervals in the offset time. This makes the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Length of offset between a value of 1 and 0 in a PPM modulated code. The length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Time between possible dither positions in a PPM pulse interval. (For pulse position modulation.) Time step of the simulation. It is an integer division of the ChipInterval. It is approximately PulseWidth/10 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. Energy in Joules of a single pulse output from the pulse generator Time between positive and negative peaks of the waveform when doublet pulse is used. Maximum delay applied to a correlator finger in the rake receiver. Ratio of simulation bandwidth to noise bandwidth of band limited noise source. The bandwidth is of the band limited noise source is 1/(2 NoiseBandWidthRatio TStep). Total power of bandwidth limited noise source in dbm. Power of interfering UWB source in db relative to desired channel power Number of bits simulated. Length of time that SpectrumAnalyzer components collect data Receiver Sensitivity with Interference Sources

37 Simulation Results The Data Display window shows the transmit pulse train over two time scales. The receiver input signal plot shows the transmit signal combined with the wide band interference. The spectra of the transmit signal and the interfering noise are also shown. Receiver Sensitivity with Interference Sources 2-31

38 Pulse Mode Test Benches Bit errors are determined by comparing the data bits input to the transmitter to those output from the receiver. An Eb/No plot shows how the BER is degraded by the wideband interference power Receiver Sensitivity with Interference Sources

39 BER versus Range The BER versus Range Test Bench simulates a UWB system with environmental factors. The simulation determines BER performance as a function of distance between the transmit and receive antennas. Antenna, propagation loss, and multipath models are provided. A single receive path correlates a reference waveform with an individual arrival of the multipath signal. The receiver front-end noise figure and bandwidth are selectable. The transmitter section of the test bench schematic is shown in Figure 2-11; the receiver section of the test bench schematic is shown in Figure To Receiver Section Figure BER versus Range Test Bench Schematic, Transmitter Section (_UWB_BER_vs_Range.dsn) BER versus Range 2-33

40 Pulse Mode Test Benches Figure BER versus Range Test Bench Schematic, Receiver Section (_UWB_BER_vs_Range.dsn) 2-34 BER versus Range

41 Pulse shapes, as well as pulse rates, amplitudes, and widths can be selected.to choose pulse position or bi-phase modulation, enable the PPM or bi-phase pulse generator component; deselect the unused component. For details, refer to BIPHASE_TX_PULSE_GENERATOR on page 2-59 or PPM_TX_Pulse_Generator on page A pseudorandom code is used to spread transmit data. The UWB_TRANSMIT_ANTENNA transmit filter represents the effects of transmit chain and antenna. For component details, refer to UWB_TRANSMIT_ANTENNA on page To simulate a UWB system that is compliant with FCC regulations for indoor communications, the transmitter pulse energy can be adjusted to produce a maximum average spectral power density of db/mhz in the 3.1 to 10.6 GHz band (-41.3 dbm/mhz is the total power radiated from an isotropic antenna). The pulse energy required to achieve the appropriate level can be determined using the Modulated Transmit Spectrum on page 2-4. UWB_ENVIRONMENT contains the propagation loss and multi-path models. For component details, refer to UWB_ENVIRONMENT on page UWB_RECEIVE_ANTENNA consists of an SBlock component that reads a file of S-parameters representing the RF frontend and antenna of the receiver. The receive antenna also contains a loss component to allow scale of the overall loss of the antenna. For component details, refer to UWB_RECEIVE_ANTENNA on page UWB_RX_LNA is used to set the receiver low noise amplifier noise figure and bandwidth to simulate receiver RF frontend performance. For component details, refer to UWB_RX_LNA on page For bi-phase modulation, the BIPHASE_RX_REFERENCE_PULSER component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when data input is all 1s. The output represents a bi-phase modulated UWB waveform. Input data bits are spread using a spreading code. For component details, refer to BIPHASE_RX_REFERENCE_PULSER on page For pulse position modulation, the PPM_RX_Reference_Pulser component outputs the same waveform as PPM_TX_Pulse_Generator when the data input is 1 with the inverse of the output when the data input is 0. The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to PPM_RX_Reference_Pulser on page BER versus Range 2-35

42 Pulse Mode Test Benches The reference pulser shaping filters apply the same filtering to the reference pulse as is applied to the transmit signal by the transmitter and receiver. For component details, refer to Ref_Pulser_Shaping_Filters on page The correlator multiplies the receive signal with a reference signal and integrates the results over a period of time. The integrator in the correlator integrates the multiplier output signal over the period of ChipInterval ChipsPerBit. It resets the integrator value to 0 and restarts the integration. For component details, refer to UWB_RX_SINGLE_FINGER_CORRELATOR on page UWB_RAKE_BIT_SLICER_UWB_Receiver serves as a bit slicer for use with a rake receiver. For component details, refer to UWB_RAKE_BIT_SLICER_UWB_Receiver on page The StopBits variable determines the number of bits to be collected by the DataOutput sink; this controls the run time of the simulation. To speed simulations that sweep the Range (distance from transmitter to receiver parameter), StopBits can be defined in a VAR equation using the piecewise linear function, so the number of bits simulated is 10 times the estimated BER at each Range. For large Range values, the BER will be higher and fewer bits will be required to determine the BER; for short Range values, simulation of more bits will be required. The user can rely on information from previously completed simulations to configure the piecewise linear function. If the SpectrumAnalyzer and TimedSink components are to be active during a simulation sweep, the user can also use a piecewise line function to optimize the TimeStop variable for the sweep. This allows collection of enough data at points of interest without producing excessively large data sets. BER versus Range Test Bench Design Parameters Name Description UWB Configuration Parameters ChipInterval ChipsPerBit Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit DitherBits Number of bits used to determine the dither position of a PPM pulse within each pulse interval. There are 2 DitherBits possible pulse positions within each PPM pulse interval. (For pulse position modulation.) TStepsPerPulseWidth TStepsPerDither DithersPerPPMBitOffset Approximate number of simulation time steps in one pulsewidth interval. Determines the number of simulation time steps between each possible position. Not used for bi-phase modulation simulations, but calculation is used to determine TStep. Number of dither positions offset between a value of 1 and 0 in a PPM modulated code. The length is given in the number of dither intervals in the offset time. This makes the offset between a 0 and 1 an integer number of possible pulse positions. Not used for bi-phase modulation simulations, but calculation is used to determine TStep BER versus Range

43 Name TStepsPerPPMBitOffset DitherTime TStep PulseWidth PulseEnergy_joule DoubletSeparation MaxFingerDelay NoiseFigure_dB RXNoiseBandwidth FilterDelay gamma Range RangePower Description Number of TStep offset between a value of 1 and 0 in a PPM modulated code. The length is given in the number of TStep long intervals in the offset time. Not used for bi-phase modulation simulations, but calculation is used to determine TStep. Time between possible dither positions in a PPM pulse interval. Parameters must be selected such that DitherTime is greater than TStep or a divide by zero error will occur. Not used for Biphase modulation simulations, but calculation is used to determine TStep. Time step of the simulation. It is an integer division of the ChipInterval. It is approximately PulseWidth/TStepsPerPulseWidth 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. Energy in Joules of a single pulse output from the pulse generator Time between the positive and negative peaks of the waveform when doublet pulse is used. (Used when doublet waveform is selected.) Maximum delay applied to a correlator finger in the rake receiver. Noise figure of receiver frontend. Noise passband of the receiver frontend. Delay applied to the integrator reset and bit slicer to allow for signal delay through filters Power of distance from the source at which signal amplitude decays. For an isotropic antenna in free space, gamma equals 2. Distance from transmitter to receiver. A base distance is multiplied by 2 RangePower in simulation sweeps of distance Multi-Path Parameters DelayTime1,..., DelayTime6 Delay1,..., Delay6 Mag0,..., Mag5 SumDelay1,..., SumDelay6 Time of arrival of each multipath component relative to the first arrival time. Number of TSteps of delay applied to each series delay in the multipath component. This is calculated such that round off errors do not accumulate Relative magnitude of each multi-path arrival. Calculates the series delays applied by the multipath component in a way that round-off errors do not accumulate. BER versus Range 2-37

44 Pulse Mode Test Benches Simulation Results The Data Display window shows the transmit signal and the receiver signal inputs. Input data bits and the receiver outputs are shown BER versus Range

45 The Range plot shows the BER of both receivers as a function of range. BER versus Range 2-39

46 Pulse Mode Test Benches Synchronization The Synchronization Test Bench simulates a UWB receiver obtaining synchronization with a received signal. To Receiver Section Figure Synchronization Test Bench (_UWB_Synchronization_Bench.dsn) 2-40 Synchronization

47 Synchronization 2-41

48 Pulse Mode Test Benches Pulse shapes, as well as pulse rates, amplitudes, and widths can be selected.to choose pulse position or bi-phase modulation, enable the PPM or bi-phase pulse generator component; deselect the unused component. For details, refer to BIPHASE_TX_PULSE_GENERATOR on page 2-59 or PPM_TX_Pulse_Generator on page A pseudorandom code is used to spread the transmit data. Band-limited noise is added to the transmit signal before it enters the receiver (for component details, refer to BAND_LIMITED_NOISE_SOURCE_UWB_Channel on page 2-55). For bi-phase modulation, the BIPHASE_RX_REFERENCE_PULSER component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when the data input is all 1s. The output represents a bi-phase modulated UWB waveform. The input data bits are spread using a spreading code. (For component details, refer to BIPHASE_RX_REFERENCE_PULSER on page 2-57.) For pulse position modulation, the PPM_RX_Reference_Pulser component outputs the same waveform as PPM_TX_Pulse_Generator when the data input is 1 with the inverse of the output when the data input is 0. (For component details, refer to PPM_RX_Reference_Pulser on page 2-66.) The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. A delay is applied to the received signal to cause the receiver to be out of synchronization with the receiver. When the reference signal to the correlator is not synchronized with the receive signal, distribution of the correlator output will be centered about 0V. When the correlator is synchronized, distribution of the correlator output signals will be centered about a positive offset voltage. The synchronization algorithm applied in this simulation adjusts the correlator timing to maximize the amplitude to the correlator output signal. The correlator output is used as feedback for coarse and fine synchronization algorithms that adjust the delay applied to the de-spreading code; this brings it into alignment with the spreading code of the receive signal. These simulations demonstrate the ability of a correlator to obtain and maintain synchronization under user-defined conditions of signal-to-noise ratio and correlator integration time. For typical simulation, the delay applied to the received signal will be a few spreading code positions. This delay is determined by the CodeOffset variable; it could be set to a very large value, but DefaultNumericStop must also be set to a large value in order for the correlator to achieve synchronization during simulation (this could require excessive time for the simulation to complete). This simulation is designed to focus on the critical time period when the correlator is a few code positions out of synchronization through the time that synchronization is achieved Synchronization

49 This simulation uses two correlators: the synchronization correlator provides synchronization feedback; the receive correlator is used to decode data after synchronization is achieved. Timing is controlled by a feedback loop around the synchronization correlator. The data transmitted is all 1s. The feedback loop adjusts the timing of the receiver reference pulse train as well as the timing of the correlator integration interval and the bit slicer. For correlator component details, refer to UWB_RX_Correlator_with_Integrator_Reset_UWB_Receiver on page The coarse synchronization block measures the average amplitude of negative polarity outputs from the correlator. If the ratio of current correlator output value to the absolute value of the average negative correlator output value is less than the value of RelSyncAmplitude, the coarse synchronization algorithm increases the delay of the correlator reference signal by the value of CoarseTimeStep. When the ratio is greater than RelSyncAmplitude, no coarse adjustment in synchronizer timing is applied. For component details, refer to Sync_Coarse_UWB_Receiver on page The fine synchronization block measures the average correlator output over a given time interval. After each averaging time interval the fine synchronization algorithm adjusts the correlator delay by plus or minus one TStep (typically, approximately 1/10th a pulse width). If the most recent averaged output value is greater than the previous value, the polarity of the delay adjustment is the same as the previous adjustment. If the most recent value recorded averaged output value is less than the previous value, the polarity of the delay adjustment is the opposite of the previous adjustment. This algorithm will optimally align the correlator reference signal with the receive signal after the coarse synchronization is achieved. For component details, refer to Sync_Fine_Tune_UWB_Receiver on page For this algorithm to achieve optimal synchronization depends on the shape of the pulse waveform. For the Gaussian monopulse waveform, the synchronization algorithm optimally aligns the received and reference waveforms. However, if the pulse shape has several oscillations (such as Gaussian Second Derivative pulse shape), there will be local correlator output maxima at offsets from optimal synchronization. There will be a range of signal-to-noise ratios for which this algorithm may synchronize one of the local maxima rather than on the optimal alignment. Simulations showing synchronization on non-optimal local maxima indicate the need to implement a higher level search algorithm for the optimal synchronization offset within a time window about the synchronization point achieved by the low-level algorithm of this simulation. Synchronization 2-43

50 Pulse Mode Test Benches Synchronization Test Bench Design Parameters Name ChipInterval ChipsPerBit DitherBits TStepsPerPulseWidth TStepsPerDither DithersPerPPMBitOffset TStepsPerPPMBitOffset DitherTime TStep PulseWidth DoubletSeparation PulseEnergy_joule NoiseBandWidthRatio NoisePower_dBm SyncIntegTime CodeOffset RelSyncAmplitude CoarseSyncStep NumFineSyncAvg StopBits Description Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit. This also determines the number of pulses integrated by the data correlator for each bit. Number of bits used to determine the dither position of a PPM pulse within each pulse interval. There are 2 DitherBits possible pulse positions within each PPM pulse interval. (For pulse position modulation.) Approximate number of simulation time steps in one pulsewidth interval. Number of simulation time steps between each possible pulse position with PPM modulation. This value is an integer. Length of offset between a value of 1 and 0 in a PPM modulated code. Length is given in the number of dither interval long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Length of offset between a value of 1 and 0 in a PPM modulated code. Length is given in number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Time between possible dither positions in a PPM pulse interval. (For pulse position modulation.) Time step of the simulation. An integer division of ChipInterval, it is approximately PulseWidth/TStepsPerPulseWidth. 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. Time between positive and negative peaks of the waveform when doublet pulse is used. (Used when doublet waveform is selected.) Total energy in Joules of a single pulse output from the PULSE_SHAPE_GENERATOR. For the Gaussian doublet pulse shape it is the energy of each individual polarity pulse in the doublet. Determines the Bandwidth of the interfering noise source. The bandwidth is equal to 1/(TStep NoiseBandWidthRatio). Power of interfering noise source in dbm. Integration time of synchronization correlator. Delay applied to the transmit signal is give by CodeOffset ChipsPerBit ChipInterval. This determines the length of the time offset that must be scanned by the receiver to obtain synchronization. If the ratio of current correlator output to the absolute average negative correlator output is less than the RelSyncAmplitude value, the coarse synchronization algorithm increases the delay of the correlator reference signal by the value of CoarseTimeStep. Size of time adjustment applied to correlator timing when coarse synchronization block determines that correlator is not synchronized. Number of samples averaged for each fine sync iteration. Number of bits that the DataOutput NumericSink will receive during simulation. This determines the overall length of the simulation Synchronization

51 Simulation Results The Data Display window shows the output value of the synchronization correlator as a function of time; when synchronization is obtained, this value will be greater than when the receiver is unsynchronized. The delay value applied to the receive reference signal as a function of time is also shown; when synchronization is achieved changes in this value should be limited to small oscillation due to the fine synchronization loop. Synchronization 2-45

52 Pulse Mode Test Benches 2-46 Synchronization

53 Rake Receiver The Rake Receiver Test Bench simulates a rake receiver in a multi-path environment. To Receiver Section Figure Rake Receiver Test Bench Schematic, Transmitter Section (_UWB_Rake_Receiver.dsn) Rake Receiver 2-47

54 Pulse Mode Test Benches Figure Rake Receiver Test Bench Schematic, Receiver Section (_UWB_Rake_Receiver.dsn) 2-48 Rake Receiver

55 To choose pulse position or bi-phase modulation, enable the PPM or bi-phase pulse generator component; deselect the unused component. Pulse shapes, as well as pulse rates, amplitudes, and widths can be selected. For details, refer to BIPHASE_TX_PULSE_GENERATOR on page 2-59 or PPM_TX_Pulse_Generator on page The transmit filter represents the effects of transmitter front-end and antenna; for details, refer to UWB_TRANSMIT_ANTENNA on page A pseudorandom bit sequence is used as the spreading code for UWB modulation. For bi-phase modulation, one bit from the spreading code is consumed per transmitted pulse. The spreading code repeat time is equal to the pulse interval multiplied by the pseudorandom bit sequence length. For pulse position modulation, the value of DitherBits determines the number of spreading code bits consumed for each transmitted pulse. The spreading code repeat time for pulse position modulation is the pulse interval multiplied by the spreading code length divided by the number of value of DitherBits. The spreading code repeat time determines the spacing of spectral lines in the modulated transmit spectrum. UWB_ENVIRONMENT contains the propagation loss and multi-path models. For component details, refer to UWB_ENVIRONMENT on page UWB_RECEIVE_ANTENNA consists of an SBlock component that reads a file of S-parameters representing the RF frontend and antenna of the receiver. The receive antenna also contains a loss component to allow scale of the overall loss of the antenna. For component details, refer to UWB_RECEIVE_ANTENNA on page UWB_RX_LNA is used to set the receiver low noise amplifier noise figure and bandwidth to simulate receiver RF frontend performance. For component details, refer to UWB_RX_LNA on page For bi-phase modulation, the BIPHASE_RX_REFERENCE_PULSER component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when data input is all 1s. The output represents a bi-phase modulated UWB waveform. Input data bits are spread using a spreading code. For component details, refer to BIPHASE_RX_REFERENCE_PULSER on page For pulse position modulation, the PPM_RX_Reference_Pulser component outputs the same waveform as PPM_TX_Pulse_Generator when the data input is 1 with the inverse of the output when the data input is 0. The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. For component details, refer to PPM_RX_Reference_Pulser on page Rake Receiver 2-49

56 Pulse Mode Test Benches The reference pulser shaping filters apply the same filtering to the reference pulse as is applied to the transmit signal by the transmitter and receiver. For component details, refer to Ref_Pulser_Shaping_Filters on page An SBlock component represents the response of the transmitter circuitry and antenna. A propagation loss model is applied with variable attenuation rates to allow modeling of different terrains and antenna configurations. Multipath reflected signals are applied, creating multiple arrivals for each pulse at varying amplitudes and delays. The rake receiver uses four fingers by default and can be expanded as necessary. Each finger correlates the receiver reference signal with an individual arrival of the multi-path signal. The correlator outputs of each finger are scaled relative to its signal-to-noise ratio. The scaled outputs of all fingers are summed. A single correlator receiver is also included to allow comparison of a single correlator with the multi-finger receiver performance. To simulate a UWB system that is compliant with the FCC regulations for indoor communications, the transmitter pulse energy can be adjusted to produce a maximum average spectral power density of db/mhz in the 3.1 GHz to 10.6 GHz band. The pulse energy required achieve the proper level can be determined using the Modulated Transmit Spectrum Test Bench design (_UWB_Modulated_Transmit_Spectrum.dsn) dbm/mhz is the total power radiated from an isotropic antenna. The StopBits variable determines the number of bits to be collected by the DataOutput sink. This controls the run time of the simulation. To speed simulations that sweep the interfering noise power, StopBits can be defined in a VAR equation using the piecewise-linear function so the number of bits simulated is 10 times the estimated BER at that noise power. For high noise power levels, the BER will be higher, and fewer bits are required to accurately determine the BER. At lower noise power levels, simulation of more bits will be required. The user can rely on information from previously completed simulations to configure the piecewise-linear function. If the SpectrumAnalyzer and TimedSink components are to be active during a simulation sweep, the user can also use a piecewise-linear function to optimize the TimeStop variable for the sweep. TimeStop determines the amount of data to be collected by these components Rake Receiver

57 Rake Receiver Test Bench Design Parameters Name StopBits TimeStop ChipInterval ChipsPerBit DitherBits TStepsPerDither DithersPerPPMBitOffset TStepsPerPPMBitOffset DitherTime TStep Description Number of bits simulated. Length of time SpectrumAnalyzer components collect data. Time between pulses. For PPM this is the nominal time between pulses. Number of pulses transmitted for each bit. Number of bits used to determine the dither position of a PPM pulse within each pulse interval. There are 2 DitherBits possible pulse positions within each PPM pulse interval. (For pulse position modulation.) Determines the number of simulation time steps between each possible position. Length of offset between a value of 1 and 0 in a PPM modulated code. Length is given in the number of dither interval long intervals in the offset time. This makes the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Length of offset between a value of 1 and 0 in a PPM modulated code. The length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. (For pulse position modulation.) Time between possible dither positions in a PPM pulse interval. (For pulse position modulation.) Time step of the simulation. It is an integer division of the ChipInterval. It is approximately PulseWidth/TStepsPerPulseWidth PulseWidth 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. DoubletSeparation NoiseFigure RXNoiseBandwidth PulseEnergy_joule MaxFingerDelay FilterDelay gamma Range RangePower DelayTime1,..., DelayTime6 Delay1,..., Delay6 Mag0,..., Mag5 Time between the positive and negative peaks of the waveform when doublet pulse is used. (Used when doublet waveform is selected.) Noise figure of the receiver frontend. Noise passband of the receiver frontend. Energy in Joules of single pulse output from the pulse generator. Maximum delay applied to a correlator finger in the rake receiver. Delay applied to the integrator reset and bit slicer to allow for signal delay through filters Power of distance from the source at which signal amplitude decays. For an isotropic antenna in free space, gamma equals 2. Distance from the transmitter to the receiver. A base distance is multiplied by 2 RangePower in simulation sweeps of distance. Time of arrival of each multipath component relative to the first arrival time. Number of TSteps of delay applied to each series delay in the multipath component. This is calculated such that round off errors do not accumulate. Relative magnitude of each multi-path arrival. Rake Receiver 2-51

58 Pulse Mode Test Benches Simulation Results The Data Display window shows the transmit signal and the receiver input signal. Input data bits and the rake and single correlator receiver outputs are shown Rake Receiver

59 The Eb/No plot shows the bit error rate of both receivers. Rake Receiver 2-53

60 Pulse Mode Test Benches Pulse Mode Test Bench Component Details Components designed specifically for pulse mode test benches are described in this section Pulse Mode Test Bench Component Details

61 BAND_LIMITED_NOISE_SOURCE_UWB_Channel Parameters Name Description Default Unit Type Range NoiseBandWidthRatio Integer ratio of the simulation bandwidth to the bandwidth of the 7 Integer >0 noise source. Simulation bandwidth is given by 1/(2 TStep). NoisePower_dBm Total rms power from the noise source. -40 Real < TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 1 Gaussian PDF noise Timed BAND_LIMITED_NOISE_SOURCE_UWB_Channel 2-55

62 Pulse Mode Test Benches BiPhase_Polarity_Select_UWB_Transmitter This component is used to trigger a positive or negative polarity pulse for bi-phase modulation. The input data bit is exclusive OR-ed with the spreading code. If the result or the exclusive OR is a 1, a pulse on the positive pulse trigger is generated; otherwise, a pulse on the negative pulse trigger is generated. Parameters Name Description Default Unit Type Range ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 ChipInterval Time between pulses 1 nsec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Data Input Data transmitted by UWB system input as binary bits Integer 2 Spreading Code Input Coding sequence used to spread data being transmitted input as binary bits. Integer Outputs 3 Positive Pulse Trigger Impulse to trigger generation of a positive polarity pulse. Float 4 Negative Pulse Trigger Impulse to trigger generation of a positive polarity pulse. Float 2-56 BiPhase_Polarity_Select_UWB_Transmitter

63 BIPHASE_RX_REFERENCE_PULSER This component outputs the same waveform as BIPHASE_TX_PULSE_GENERATOR when the data input is all 1s. The waveform output from this test block represents a bi-phase modulated UWB waveform. The input data bits are spread using a spreading code. The pulse shape output is determined by selecting PULSE_SHAPE_GENERATOR sub-components; for details, refer to PULSE_SHAPE_GENERATOR on page Subnetwork Parameters Name Description Default Unit Type Range ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 ChipInterval Time between pulses 1 nsec Time Real >0 PulseWidth Width of output pulse 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules. 1e-12 Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform 350 psec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 BIPHASE_RX_REFERENCE_PULSER 2-57

64 Pulse Mode Test Benches Inputs 1 Spreading Code Input Coding sequence used to spread data being transmitted input as binary bits. Integer Outputs 2 Pulse Output Outputs pulse with shape determined by which pulse generator subcomponent is selected. Float 2-58 BIPHASE_RX_REFERENCE_PULSER

65 BIPHASE_TX_PULSE_GENERATOR The BIPHASE_TX_PULSE_GENERATOR output represents a bi-phase modulated UWB waveform. Input data bits are spread using a spreading code. The pulse shape output is determined by selecting sub-components of PULSE_SHAPE_GENERATOR (see PULSE_SHAPE_GENERATOR on page 2-71). Subnetwork Parameters Name Description Default Unit Type Range ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 ChipInterval Time between pulses 1 nsec Time Real >0 PulseWidth Width of output pulse 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules. 1e-12 Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform 350 psec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Data Input Data transmitted by UWB system input as binary bits. Integer 2 Spreading Code Input Coding sequence used to spread data being transmitted input as binary bits. Integer BIPHASE_TX_PULSE_GENERATOR 2-59

66 Pulse Mode Test Benches Outputs 3 Pulse Output Outputs pulse with shape determined by which pulse generator subcomponent is selected and polarity determined by data and spreading code. Float 2-60 BIPHASE_TX_PULSE_GENERATOR

67 INTERFERENCE_SOURCE_80211a_UWB_Channel The waveform for the a source is read from data set file WLAN_80211a_Order11.ds. The interfering source operates at 100% duty cycle. The baseband signal is upsampled and downsampled using a ratio that adjusts its time step to be equal to TStep. The baseband waveform is a quadrature mixed carrier that is also represented in baseband form; the modulated signal at carrier frequency is represented in baseband form in the simulation. Parameters Name Description Default Unit Type Range wlanpower_dbm Power level of the a interference source in dbm 0 Real < wlanfreq Center frequency of the a interference source 2.412e9 Frequency Real >0 TStep Time step of the simulation 10 psec Time Real >0 Outputs 1 Output Output from a source Timed INTERFERENCE_SOURCE_80211a_UWB_Channel 2-61

68 Pulse Mode Test Benches INTERFERENCE_SOURCE_80211B_UWB_Channel The waveform for the b source is read from data set file WLAN_80211b_8Xoversample.ds. The interfering source operates at 100% duty cycle. The baseband signal is upsampled and downsampled using a ratio that adjusts its time step to be equal to TStep. The baseband waveform is a quadrature mixed carrier that is also represented in baseband form; the modulated signal at carrier frequency is represented in baseband form in the simulation. Parameters Name Description Default Unit Type Range wlanpower_dbm Power level of the b interference source in dbm 0 Real < wlanfreq Center frequency of the b interference source 2.412e9 Frequency Real >0 TStep Time step of the simulation 10 psec Time Real >0 Outputs 1 Output Output from b source Timed 2-62 INTERFERENCE_SOURCE_80211B_UWB_Channel

69 MultipathDelayBlock_UWB_Channel Delay inputs are the incremental delays from one multi-path input to the next. Relative magnitudes of each arrival are applied. Multi-path delay blocks can be connected in series to produce as many arrival times as required. Series connection uses Single Delayed Output pin 2. Delay1 through Delay5 and Mag0 through Mag4 affect the delay paths; when one MultipathDelayBlock_UWB_Channel is used, set Delay6=1 and Mag5=1, and connect as in UWB_ENVIRONMENT on page For low pulse-rate applications where arrivals of sequential pulses do not overlap, it may be necessary to include arrivals within the integration window of the receiver correlators only. Note Multipath terms can be defined using the IEEE P SG3a study group standard model based on a model developed by Saleh and Valenzuela (S-V) which includes a log-normal decay of the clusters along with a log-normal decay of rays within each cluster. See the SG3A Channel Modeling Sub-committee Report (Final), IEEE P /490r0-SG3a, December Parameters Name Description Default Type Range Delay1,..., Delay6 Number of TSteps of delay applied to each multipath arrival 1 Integer < Mag0,..., Mag5 Relative magnitude of each multipath arrival. The rake receiver uses these values to set the polarity of each correlator finger. 1 Real < Inputs 1 Input Transmit waveform Float MultipathDelayBlock_UWB_Channel 2-63

70 Pulse Mode Test Benches Outputs 2 Single Delayed Output Input waveform delayed by the value of SumDelay5 TStep Float 3 Combined Multipath Output Input waveform summed with SumDelay1 TStep through SumDelay5 TStep Float with respective magnitudes applied MultipathDelayBlock_UWB_Channel

71 PPM_MOD_UWB_Transmitter PPM_Mod_UWB_Transmitter determines the timing of a PPM modulated pulse stream. DitherBits determines the number of bits consumed from the spreading input for each data bit input. The time delay is calculated by multiplying TStepsPerDither by the integer value of the spreading code bits consumed. TStepsPerPPMBitOffset is added to the delay value if the data bit is 1. The delay output is an integer indicating the TSteps delay to be applied to the pulse. Parameters Name Description Default Unit Type Range TStepsPerPPMBitOffset Length of offset between a value of 1 and 0 in a PPM modulated code. Length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. 1 Integer >0 ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 DitherBits TStepsPerDither Number of bits used to the dither position of a PPM pulse within each pulse interval. 2 DitherBits pulse positions are possible within each PPM pulse interval. Determines the number of simulation time steps between each possible position 5 Integer >0 5 Integer >0 ChipInterval Time between pulses 1 nsec Time Real >0 PulseWidth Width of output pulse 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules. 1e-12 Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform. Only used for doublet pulses. 350 psec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Spreading Code Input Coding sequence used to spread data being transmitted input as binary bits. Integer Outputs 2 Pulse Output Outputs pulse with shape determined by which pulse generator subcomponent is selected. Float PPM_MOD_UWB_Transmitter 2-65

72 Pulse Mode Test Benches PPM_RX_Reference_Pulser PPM_RX_Reference_Pulser outputs a waveform that is the sum of the pulse waveform produced by PPM_TX_PULSE_GENERATOR when the data input is 1 with the inverse of the output when the data input is 0. The output represents a pulse position modulated UWB waveform. The input data bits are spread using a spreading code. The pulse shape output is determined by selecting sub-components of PULSE_SHAPE_GENERATOR; for details, refer to PULSE_SHAPE_GENERATOR on page Subnetwork Parameters Name Description Default Unit Type Range TStepsPerPPMBitOffset Length of offset between a value of 1 and 0 in a PPM modulated code. The length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions. 1 Integer >0 ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 DitherBits Number of bits used to the dither position of a PPM pulse within each pulse interval. 2 DitherBits pulse positions are possible within each PPM pulse interval. 5 Integer > PPM_RX_Reference_Pulser

73 Name Description Default Unit Type Range TStepsPerDither Determines the number of simulation time steps between each possible position. 5 Integer >0 ChipInterval Time between pulses 1 nsec Time Real >0 PulseWidth Width of output pulse 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules. 1e-12 Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform. Only used for doublet pulses. 350 psec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Spreading Code Input Coding sequence used to spread data being transmitted input as binary bits. Integer Outputs 2 Pulse Output Outputs pulse with shape determined by which pulse generator subcomponent is selected. Float PPM_RX_Reference_Pulser 2-67

74 Pulse Mode Test Benches PPM_TX_Pulse_Generator The PPM_TX_Pulse_Generator output represents a pulse position modulated UWB waveform. Input data bits are spread using a spreading code. The pulse shape output is determined by selecting sub-components of PULSE_SHAPE_GENERATOR; for details, refer to PULSE_SHAPE_GENERATOR on page Subnetwork Parameters Name Description Default Unit Type Range TStepsPerPPMBitOffset Length of offset between a value of 1 and 0 in a PPM modulated code; Length is given in the number of TStep long intervals in the offset time. This make the offset between 0 and 1 an integer number of possible pulse positions 1 Integer >0 ChipsPerBit Number of pulses transmitted for each bit 1 Integer >0 TStepsPerDither DitherBits Determines number of simulation time steps between each possible position. Number of bits used to the dither position of a PPM pulse within each pulse interval. 2 DitherBits pulse positions are possible within each PPM pulse interval. 1 Integer >0 5 Integer >0 ChipInterval Time between pulses 1 nsec Time Real >0 PulseWidth Width of output pulse 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules. 1e-12 Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform 350 psec Time Real >0 TStep Time step of the simulation 10 psec Time Real > PPM_TX_Pulse_Generator

75 Inputs 1 Data Input Data transmitted by UWB system input as binary bits. Integer 2 Spreading Code Input Coding sequence used to spread data being transmitted input as binary bits. Integer Outputs 3 Pulse Output Outputs pulse with shape determined by which pulse generator subcomponent is selected. Float PPM_TX_Pulse_Generator 2-69

76 Pulse Mode Test Benches PropagationLoss A propagation loss model is applied with variable attenuation rates to allow modeling of different terrains and antenna configurations. The value of gamma determines the rate of attenuation of the signal with distance. For free space, gamma equals 2. Parameters Name Description Default Unit Type Range gamma Power of distance from the source at which signal amplitude decays. In free space, gamma equals 2. 2 Real >0 Range Distance from transmitter to receiver 3 Distance Real >0 do Reference range for propagation loss. There is 0 db attenuation at the reference range. 3 Distance Real >0 numwalls Number of walls between transmit and receive antennas 0 Integer >or=0 LossWall Attenuation of signal by each wall 10 db Real >0 numfloors Number of floors between transmit and receive antennas 0 Integer >or=0 LossFloor Attenuation of signal by each floor 10 db Real >0 Inputs 1 Input Transmit waveform Float Outputs 2 Output Attenuated copy of input waveform Float 2-70 PropagationLoss

77 PULSE_SHAPE_GENERATOR To select a pulse shape, push into the PULSE_SHAPE_GENERATOR component; enable the component for the desired pulse shape; disable the unused components. In simulations, TStep is approximately PulseWidth/10. One pulse waveform is output each time the input signal amplitude equals 1. The total waveform width is PulseWidth. When pulses overlap, the first pulse is truncated. Subnetwork Inputs 1 Trigger Input An input impulse with magnitude 1 triggers PULSE_SHAPE_GENERATOR to output pulse Float Outputs 2 Pulse Output Outputs pulse with shape determined by pulse generator subcomponent Float PULSE_SHAPE_GENERATOR 2-71

78 Pulse Mode Test Benches The GAUSSIAN_DOUBLET_UWB_Transmitter generates a pair of Gaussian monopulse waveforms of opposite polarity. Parameters Name Description Default Unit Type Range PulseWidth Width of output pulse at 1/2 maximum amplitude of each of Gaussian monopulses that make up the doublet 250 psec Time Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules. This value will not be calibrated when the individual pulses of the doublet overlap 1e-12 Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Trigger Input An input impulse with magnitude 1 triggers the output of a Gaussian doublet pulse Float Outputs 2 Pulse Output Outputs Gaussian doublet pulse waveform Float The GAUSSIAN_FIRST_DERIVATIVE_UWB_Transmitter outputs a pulse with the shape of the first derivative of a Gaussian monopulse when a 1 is input. Parameters Name Description Default Unit Type Range PulseWidth Width of output pulse at 1/2 maximum amplitude of Gaussian monopulse of which the output waveform is a first derivative 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules 1e-12 Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Trigger Input An input impulse with magnitude 1 triggers the output of a Gaussian first derivative pulse Float 2-72 PULSE_SHAPE_GENERATOR

79 Outputs 2 Pulse Output Outputs Gaussian first derivative waveform Float The GAUSSIAN_MONOPULSE_UWB_Transmitter outputs a Gaussian-shaped monopulse when a 1 is input. Parameters Name Description Default Unit Type Range PulseWidth Width of output pulse at 1/2 maximum amplitude 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules 1e-12 Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Trigger Input An input impulse with magnitude 1 triggers the output of a Gaussian monopulse Float Outputs 2 Pulse Output Outputs pulse with single Gaussian shaped pulse Float The GAUSSIAN_SECOND_DERIVATIVE_UWB_Transmitter outputs a pulse with the shape of the second derivative of a Gaussian monopulse when a 1 is input. Parameters Name Description Default Unit Type Range PulseWidth Width of output pulse at 1/2 maximum amplitude of Gaussian monopulse of which the output waveform is a second derivative 250 psec Time Real >0 PulseEnergy_joule Total energy of the output pulse in Joules 1e-12 Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Trigger Input An input impulse with magnitude 1 triggers the output of a Gaussian second derivative pulse Float PULSE_SHAPE_GENERATOR 2-73

80 Pulse Mode Test Benches Outputs 2 Pulse Output Outputs Gaussian second derivative waveform Float 2-74 PULSE_SHAPE_GENERATOR

81 PULSE_TRIGGER_UWB_Transmitter PULSE_TRIGGER_UWB_Transmitter produces an impulse every ChipInterval period. The input delay value is then applied to the impulse before it is output. Parameters Name Description Default Unit Type Range ChipInterval Time between pulses 1 nsec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Input Delay Value Number of TSteps of delay to be applied to each pulse. Integer Outputs 2 PPM Trigger Output A pulse position modulated impulse used to trigger the pulse shape generator. Float PULSE_TRIGGER_UWB_Transmitter 2-75

82 Pulse Mode Test Benches Rake_Finger_UWB_Receiver Global Variables Name Description Default Unit Type Range DelayFinger Delay time of this finger 0 sec Float >=0 MaxFingerDelay Delay of rake finger with the maximum value sec Float >=0 TStep Time step of simulation sec Float >=0 Polarity Polarity of multipath component 1 Integer -1, Rake_Finger_UWB_Receiver

83 Ref_Pulser_Shaping_Filters The reference pulser shaping filters apply the same filtering to the reference pulse as is applied to the transmit signal by the transmitter and receiver. Subnetwork Global Variables Name Description Default Unit Type Range TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Input Output of receive reference pulse Timed Outputs 2 Output Output of receive reference pulse signal with series combination of transmit and receive filtering applied. Timed Ref_Pulser_Shaping_Filters 2-77

84 Pulse Mode Test Benches Sync_Coarse_UWB_Receiver Sync_Coarse_UWB_Receiver compares the correlator integrator output to the magnitude of the average negative value of the correlator integrator output. If the most recent correlator output is less than RelSyncAmplitude times the average negative correlator output value the coarse sync adjustment outputs 1; otherwise, it outputs 0. The Sync_Coarse algorithm stops incrementing the time offsets when the correlator integrator output exceeds the threshold level. Parameters Name Description Default Type Range RelSyncAmplitude If the ratio of current correlator output value to the absolute value of the average negative correlator output value is less than the value of RelSyncAmplitude, the coarse synchronization algorithm increases the delay of the correlator reference signal by the value of CoarseTimeStep. 1.5 Float >0 Inputs 1 In Correlator output value Float Outputs 2 Out If coarse sync adjustment is to be applied, it is 1.; otherwise, it is 0. Integer 2-78 Sync_Coarse_UWB_Receiver

85 Sync_Fine_Tune_UWB_Receiver Sync_Fine_Tune_UWB_Receiver compares a time average of the correlator integrator output to the previous value of time averaged correlator output. After collecting each time average sample it either increments or decrements the timing of the correlator by one TStep. If the most recent averaged correlator output value is greater than the previous, the offset delay increment is in the same direction as the previous; if the most recent averaged correlator output value is less than the previous, the offset delay increment is in the opposite direction of the previous. Parameters Name Description Default Type Range NumFineSyncAverage Number of inputs to average 32 Integer >1 Inputs 1 In Correlator output value Float Outputs 2 Out Determines the direction of the fine synchronization adjustment by outputting 1 or -1. Integer Sync_Fine_Tune_UWB_Receiver 2-79

86 Pulse Mode Test Benches UWB_BIT_SLICER_UWB_Receiver The bit slicer captures the correlator integrator output value immediately before the integrator resets. This value is used to determine whether the output is a 0 or 1 bit. Parameters Name Description Default Unit Type Range ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 ChipInterval Time between pulses 1 nsec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Input Signal from output of correlator integrator. Float Outputs 2 Bits Output Demodulated data bits Integer 2-80 UWB_BIT_SLICER_UWB_Receiver

87 UWB_ENVIRONMENT This subnetwork contains the propagation loss and multi-path models. Subnetwork Global Variables Name Description Default Unit Type Range TStep Time step of the simulation 10 psec Time Real >0 Delay1,2,3,... Mag0,1,2,... gamma Number of TSteps of delay applied to each series delay in the multipath component. This is calculated such that round off errors do not accumulate. Relative magnitude of each multi-path arrival. Power of distance from the source at which signal amplitude decays. For an isotropic antenna in free space, gamma equals 2. Inputs 1 Input Outputs of transmitter antenna. Timed Outputs 2 Output Transmit signal with multipath components and loss relative to the signal level at do applied. Timed UWB_ENVIRONMENT 2-81

88 Pulse Mode Test Benches UWB_Interference_Source The component provides a second UWB signal source for use as a wideband interfering signal. Parameters Name Description Default Unit Type Range TStepsPerPPMBitOffset Number of TStep intervals between 1 and a 0 position in a PPM pulse interval 50 Integer >0 ChipsPerBit Number of pulses transmitted for each bit 1 Integer >0 ChipInterval Time between pulses. For PPM this is the nominal time between pulses. 1 nsec Time Real >0 TStepsPerDither DitherBits Determines the number of simulation time steps between each possible position. Number of bits used to the dither position of a PPM pulse within each pulse interval. 2 DitherBits pulse positions are possible within each PPM pulse interval. 5 Integer >0 5 Integer >0 PulseWidth 1/2 amplitude pulsewidth of a Gaussian monopulse output. For the Gaussian derivative pulse shapes, this is the 1/2 amplitude pulsewidth of the Gaussian monopulse from which it is derived. 100 psec Time Real >0 DoubletSeparation Time between the positive and negative peaks of the waveform when doublet pulse is used. (Used when doublet waveform is selected.) 400 psec Time Real >0 PulseEnergy_joule Energy in Joules of single pulse output from the pulse generator. 1e-12 Real >0 Outputs 1 Output Output a UWB waveform Time 2-82 UWB_Interference_Source

89 UWB_RAKE_BIT_SLICER_UWB_Receiver UWB_RAKE_BIT_SLICER_UWB_Receiver performs a function similar to UWB_BIT_SLICER_UWB_Receiver. Both bit slicers sample the integrator output at the last timestep before the integrator is reset in each bit interval; the polarity of the sampled integrator output is used to determine the value of the bit. In the Rake receiver, the signal from each receiver finger is delayed to align it with the signal from the Rake finger synrhonized with the greatest delay arrival being received. UWB_RAKE_BIT_SLICER_UWB_Receiver uses the value of MaxFingerDelay to adjust the sampling time by the amount of additional delay applied to the first signal arrival. (In UWB_BIT_SLICER_UWB_Receiver, the integrator sampling time is fixed in the bit interval because variable delays are not present in the test benches that use it.) Parameters Name Description Default Unit Type Range ChipsPerBit Number of pulses transmitted for each bit 1 Integer >1 ChipInterval Time between pulses 1 nsec Time Real >0 MaxFingerDelay Largest finger delay 1 nsec Time Real >O TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Input Signal from output of correlator integrator. Float Outputs 2 Bits Output Demodulated data bits Integer UWB_RAKE_BIT_SLICER_UWB_Receiver 2-83

90 Pulse Mode Test Benches UWB_RECEIVE_ANTENNA This component consists of an SBlock component that reads a file of S-parameters representing the RF frontend and antenna of the receiver. The receive antenna also contains a loss component to allow scale of the overall loss of the antenna. S-parameters can be measured using a network analyzer. In the default setup, they are created by conducting RF simulations of a series of filters. HighPassFilter_RFsim.dsn is used to generate the default S-parameter file. After reading the S-parameters from the file, the SBlock component produces the equivalent impulse response for use in ADS Ptolemy simulations. For a practical impulse response to be produced, a high-frequency cutoff lowpass filter must be applied when S-parameters for a highpass filter are generated. Note The SBlock N value must be large enough for the filter impulse response to adequately decay. The impulse response will be truncated after a time of N TStep. Using the lowest acceptable value of N will speed simulation. A receive antenna can capture only a portion of this energy; the portion of the total radiated power that a receive antenna can capture is determined by the receive antenna aperture, the distance between transmit and receive antennas, and the antenna gains. The receive antenna is modeled using an additional SBlock component and an attenuator. The receive antenna contains a 1/frequency roll-off term to account for the reduction of antenna aperture with frequency. An additional attenuator is applied to adjust the total loss of the antenna at each frequency to the expected value at 3 meters. For example, the antenna aperture at 5.5 GHz is given by the equation λ 2 A e = Π λ is the signal wavelength and the expected aperture loss of the antenna at three meters is given by the equation ApertureLoss = 10log A e Π 3m UWB_RECEIVE_ANTENNA

91 If the directional gain of the antenna relative to an isotropic antenna is 0, then at 5.5 GHz the signal level the receive antenna delivers to the receiver is 57 db below the total transmit power at 3 meters. The loss of the default receiver SBlock component is 45 db at 5.5 GHz, so 12 db of loss is applied by the attenuator. To adjust the signal level for distances other than 3 meters, the propagation loss model is applied with do equal to 3 meters. The signal from the receive antenna goes to an amplifier; the noise figure of this amplifier can be set by the user. A lowpass filter following the amplifier limits the noise bandwidth of the receiver frontend. For more details regarding generating S-parameter files, refer to UWB_TRANSMIT_ANTENNA on page Subnetwork Global Variables Name Description Default Unit Type Range TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Input Input to receive antenna Timed Outputs 2 Output Receive antenna input waveform modified by front-end and antenna characteristics. Signal level is adjusted to account for amount of energy capture in antenna aperture at distance do. Timed UWB_RECEIVE_ANTENNA 2-85

92 Pulse Mode Test Benches UWB_RX_Correlator_UWB_Receiver This component provides multiple correlators for receiving arrivals of a multipath signal. Each correlator multiplies the received signal by an appropriately delayed reference signal. The integrator in the correlator integrates the multiplier output signal over the period of ChipInterval ChipsPerBit. It resets the integrator value to 0 and restarts the integration. The outputs of each correlator are scaled relative to its signal-to-noise ratio, and the outputs of all correlators are summed. Parameters Name Description Default Unit Type Range ChipsPerBit Number of pulses transmitted for each bit. 1 none Integer >1 ChipInterval Time between pulses. 1 nsec Time Real >0 TStep Time step of the simulation 10 psec Time Real >0 Inputs 1 Antenna Input UWB receiver input waveform Float 2 Reference Pulse Input Reference pulse waveform for correlator Float Outputs 3 Output Scaled and combined output from all correlator fingers Float 2-86 UWB_RX_Correlator_UWB_Receiver

93 UWB_RX_Correlator_with_Integrator_Reset_UWB_Receiver This correlator multiplies the receive signal with a reference signal and integrates the results over a period of time. The integrator in the correlator integrates the multiplier output signal between >1 values at the Reference Pulse Input pin 2; it resets the integrator value to 0 and restarts the integration when a pulse is received on this pin. Inputs 1 Antenna Input UWB receiver input waveform Float 2 Reference Pulse Input Reference pulse waveform for correlator Float 4 Integrator Reset Input Integer Outputs 3 Output Output from correlator integrator Float UWB_RX_Correlator_with_Integrator_Reset_UWB_Receiver 2-87